Anorexia nervosa is characterized by a disturbed body image, the marked diminution of food intake in the obsessive pursuit of thinness, a stereotypic rigidity and perfectionism, and frequent mood and neuroendocrine disturbances. After weight restoration, there is reduced severity of these abnormalities but they may not normalize. The relative contribution of neurotransmitter(s) abnormalities to the persistent pathophysiology of this disorder is unclear. There are reasons to postulate that a disturbance of brain serotonin (5-HT) pathways may be contributory. First, serotonin pathways contribute to the modulation of appetite, obsessive-compulsive traits, mood, and neuroendocrine function. Second, preliminary data show that anorexics studied after long-term (a mean of 30 months) weight normalization had elevated levels of CSF 5-HIAA, the major serotonin metabolite. A better understanding of the neurobiologic mechanisms underlying persistent abnormalities of behavior could contribute to a more effective treatment strategy for this disorder. There are several aims to this study. First, we hypothesize that long-term weight-restored anorexics will show evidence of increased serotonin activity. We will attempt to confirm and extend our finding of increased CSF 5-HIAA in these subjects. We also hypothesize that the double-blind placebo-controlled oral administration of m-CPP, a serotonergic agonists, will exacerbate obsessional and anxious symptoms, and reduce caloric consumption in anorexics compared to controls. Second, we hypothesize that a high incidence of life-time and current anxiety disorders and sub- clinical anxious and obsessional traits occur in long-term weight-restored anorexics. We will assess each subject's level of psychopathology and overall psychological functioning on admission to the study. Finally, we will determine whether differences in serotonin activity exist between patients with food restricting vs. bulimic subtypes of anorexia nervosa. Twenty-six long-term weight-restored anorexics and twenty-six matched controls will be admitted to a research laboratory for five days. Psychiatric assessment will be performed double-blind crossover administration of m-CPP/placebo will be performed on days three an five. The application of these combined methods will aid in the determination of whether alterations in serotonergic function and anxious and obsessional features represent trait-related disturbances in anorexia nervosa.